Synchronizing clock system



Dec. 17, 1929. J. w. BRYCE ET AL SYNCHRONIZING CLOCK SYSTEM Filed June23, 1925 Emmi A v n n m w M m My M Q WMHQ M a f W W MEN! R, I] I1. WWW3K W Patented Dec. 17, 1929 UNITED STATES PATENT orrlcr.

JAMES W. BRYCE, OF BLOOMFIELD, NEW JERSEY, AND CHARLES H. GETZ, OFCLEVE- LAND, OHIO, ASSIGNORS TO INTERNATIONAL TIME RECORDING COMPANY 01'NEW YORK, OF ENDICOTT, NEW YORK, A CORPORATION OF NEW YORK SYNCHRONIZINGCLOCK SYSTEM Application filed June 23, 1925. Serial No. 38,954.-

This invention relates to systems for actuating secondary clocks by amaster cloclrand to the accomplishment of maintaining all of the clocksin the system in synchronism with the master clock.

The present invention is directed to actuation and synchronization ofsecondary clocks under the control of a master clock by the agency ofelectrical energy, and has for its object to utilize for these purposeselectrical energy of two different voltages; the higher one of thesevoltages to be effective during one period of operation and the lowerone to be effectiveduring another period of operation.

Another object is to produce an electrically operated clocksynchronizing system involving the use of a minimum number of parts andwith as few Wires as possible.

Further and other objects of the present invention will be pointed outhereinafter in the accompanying specification and claims and shown inthe drawings which by way of illustration show a preferred embodiment ofour invention.

In the drawings:

Fig. 1 is a view showing the pertinent parts and wiring of a masterclock in cooperative relation to the wiring diagram of a completesystem.

Fig. 2 is a view of the minute arbor driving means of the secondaryclocks used in the system.

Master clock The master clock in its general details may be of anydesired form. For example, it may be that shown in United States PatentNo. 1,390,018. Referring to Fig. 1, the master clock includes the usualtime train adapted to drive the minute arbor 10 which makes onerevolution per hour. The usual verge mechanism 11 is provided. Fixed tothe minute shaft are a pair of cams 12, 13, which cams are shaped andpositioned to control a pair of contacts 14. Preferably the arrangementof parts is such that the contacts 14 are closed for the synchronizingperiod and opened at other times. It will be obvious, however, that by aproper rearrangement of the associated parts of the system these camcontacts could operate in a reverse manner opening in the synchronizingperiod and closing at other times.

In the present and preferred embodiment we provide for a synchronizingperiod commencing just after the minute hand of the master clock isforty-four minutes after the hour and terminating ust prior tothesixtieth minute, for reasons which will hereinafter appear.

Also fixed to the minute arbor 10 is a cam 15 which is adapted tocontrol the opening and closing of a contact 16. In the preferredembodiment contact 16 is arranged to close just after the fifty-ninthminute position and open at approximately fifty-nine and a half. For aproper functioning of the apparatus the contacts 16 should open justbefore contacts 14 open at the end of the synchronizing period.

In addition, the master clock is provided with the usual minute impulsecontacts 17 which are controlled in the usual way from a a minute cam 18or otherwise as is the custom in clocks of this sort.

For advancing or stepping forward the secondaries we provide quickacting contacts 19 and preferably operate these contacts by attachingone of them to the verge mechanism 11. These contacts 19 will close atevery swing of the pendulum if a pendulum movement is employed.

The contacts may be mounted on the master clock according to well knownmeans, as for example, similarly to those disclosed in the United Statesapplication Serial No. 722,439, filed June 26, 1924.

Secondary clock The secondary clock shown in Fig. 2 is of conventionalform and it includes a minute arbor shaft 20 which makes one revolutionper hour. This shaft is preferably advanced by means of an impulsemagnet 21 which acts through the usual ratchet wheel 22 to advance theminute arbor 20 step by step each time the magnet 21 receives an impulsefrom the master clock. Carried by the minute arbor 20 on each secondaryclock we provide a synchronizing cam 23. Cooperating with this cam is acontact device of any desired form here shown as including a blade 24adapted to close contacts 25 when the raised portion of the cam is underthe blade 24 and to close contacts 26 when the blade 24 is on the lowportions of the cam. The cam 23 is so timed that when the minute hand ofthe clock is opposite the fifty-ninth minute the blade 24 has justfallen off the high point 27 of the cam 23 breaking contact 25 andmaking con tact 26. The cam rise 28 in the present embodimentof theinvention is disposed substantially 180 around the cam from the dropofipoint 27 so that at twenty-nine minutes after the hour or slightlythereafter contacts 25 are closed and contacts 26 will be opened. Theparts are so arranged that at no time except momentarily during theshifting of blade 24 are both contacts 25 and 26 open.

Referring to the circuit diagram, current is supplied to the system froma battery, one end of which is grounded, the other end havingconnections to the master clock and to the secondary clocks through alead 30. Another lead 31 is connected to the battery so as to include afewer number of cells in circuit. It is evident that lead 30 is under ahigher voltage than lead 31 and the determination of whether a high orlow voltage is to be i1npressed across the secondary clocks is dependentu on the position of switch 29, which position ears a definite timerelation to the master clock as will be hereinafter pointed out.

It is apparent that either direct current or alternating current can beused to operate this system and an auto-transformer connected to analternating source of current, not shown, is illustrated. In thisillustration, lead 30 is the high tension line and lead 31 is the lowtension line corresponding with leads 30 and 31 respectively, of thedirect current system.

In the present system, one end of the source of electrical energy isgrounded at C at all times, and the so-called C circuit forms a commonreturn for the secondary clocks which may be metallic, if desired, whichis ordinarily the case in clock systems of this class. For simplicity inthe present description a ground return for the master and secondaryclocks is utilized.

Normal operation The first operation to be described will be the normalminute impulse operation for controlling the secondary clocks. Forclarity it will be assumed that all of the clocks at this moment are ata position somewhere between the hour reading and forty-four minuteslater.

The circuits of the master clock always remain across the high voltageline, and current is taken from the battery over wires 32, 33 and 34,through minute contacts 17, wire 35,

' timed to close.

master relay coil 36, wire 37, and back through the ground to thebattery. This periodic flow of current energizes the master relay coil36 once per minute attracting relay armature 38 and causing the currentto flow from the high voltage line 30 through switch 29, line A,arn'iature 38, feed line 39, either contact 25 or contact 26, arm 24 andto the clock impulse magnet coil 21 and back through the common groundreturn C to the battery. Thus each minute the secondary clocks areadvanced in step with the master clock.

The high voltage available during this period enables the secondaryclocks to be actuated without interruption no matter which of contacts25 or'26 is closed. Vhen contact 25 is closed, current is taken fromfeed line 39 through branch line 40, and when contact 26 is closedcurrent is taken from feed line 39 through a resistance 41. In eithercase, the strength of the current is sufficient to operate magnets 21.

Synchronization The synchronizing period starts just after theforty-fourth minute when contacts 14 are This causes current to flowfrom high voltage line 30, through wires 32, 33, 42 and contacts 14 nowclosed, synchronizing relay coil 44 and back to the battery. The 9energization of synchronizing relay coil 44 attracts the armature ofswitch 29 thereby throwing the secondary clock circuit over to the lowvoltage line 31. This position of switch 29 is maintained until justprior to the sixtieth minute by reason of the continued energization ofcoil 44. During this period the secondary clocks which are on time orslow are advanced step by step on each minute by the minute impulses ofmagnet coil 21 caused by the impulse of current from the low voltageline 31 through line A, armature 38, line 39, branch 40, contact 25,magnet coil 21, and ground C. The secondary clocks that were fast willhave stopped at the hour position, for in these clocks contacts 25 willhave opened and resistance 41 will have been thrown into the circuit bythe closing of contact 26. Resistance 41 is designed to cut down thecurrent flowing under the low voltage impression to such an extent asnot to be effective to operate electromagnet 21.

Hence, between the sixtieth and fortyfourth minute as indicated by themaster clock when the high voltage lines are connected with thesecondary clocks, current will flow through the secondary clocks ofsuflicient strength to energize magnet coil 21 on each minute impulse,whichever one of contacts 25 and 26 is closed. However, during thesynchronizing period starting just after the forty-fourth minute onlythe secondary clocks having contacts 25 closed will be actuated by theminute and acceleration impulses hereinafter described. Those havingcontacts 26 lit closed will stop because the current will not be ofsufiicient strength to actuate the coil magnets 21. f

In the diagram three secondary clocks are shown marked respectively X, Yand Z. Clock X is assumed to be on time with its minute hand inagreement with the master clock. Clock-Y is assumed to be fifteenminutes fast and clock Z fifteen minutes slow. Synchronizing cam 28 ofclock X is about the center of its high portion thus closing contacts2'5. Cam 23 of the Y or fast clock has reached such position that blade24 has dropped off step 27 closing contacts 26 and opening contacts 25.Cam 23 of the Z or slow clock has just passed the rise and has reclosedcontacts 25 and has opened contacts 26.

For the reasons previously explained, during the period ofsynchronization, impulses of sufficient strength to energize magnet coil21 can be delivered to a secondary clock only when branch 40 is in itscircuit and this only occurs when contact 25 is closed. Clock Y willtherefore remain stationary until the end of the synchronizing period.Clocks X and Z, on the other hand, are in such position that contacts 25are closed and they therefore are in condition to receive minuteimpulses during the synchronizing period. The clocks X and Z then stepalong in the usual way,

receiving the normal impulses every minute until the end of thesynchronizing period is reached.

Just after the fifty-ninth minute, as indicated by the master clock, thecam 15 reaches a position to close the contacts 16. Current now flowsfrom the source 30 over wire 32,

-wire 46, contacts 16, wire 47, contacts 19 to wire 35 and master relaycoil 36, wire 37, and back to the source. The contacts 19 close incomparatively rapid succession, for example, once every two seconds andenergize coil 36 a plurality of times which attracts armature 38 aplurality of times thereby sending a succession of fast or accelerationimpulses over wire A. It will be understood that on clock X which is ontime, contacts 25 will have opened just after the fifty-ninth impulseand before contacts 16 were closed, thereby preventing the fast step-upimpulses from effecting it. Clock Z. on the other hand, will have theparts in such position that contacts 25 are closed so that the fastimpulses are received by it which causes the clock to be stepped forwardor accelerated to advance the synchronizing cam until it reaches aposition to open contacts 25. All of the clocks X, Y and Z are now insynchronism with the master clock. After contacts 19 have sent the.selected number of fast impulses, contacts 16 will open thus renderingcontacts 19 ineffective to send further impulses. Shortly after contacts16 open and just before the sixtieth minute impulse, contacts 14 willopen thus (file-energizing the synchronizing relay coil 44, releasingthe armature of switch 29 and allowing the switch to throw the secondaryclock -Would be behind time a greater number of minutes than there areacceleration impulses furnished by the master clock, it would still belate at the hour impulse and contacts 25 would not have opened. Thisclock would still continue to operate, however. On the next hour thisdelinquent clock would be brought into synchronism with the others, asalready described. The timing of the various cams in the systemdisclosed herein has been found satisfactory to maintain all clocks insynchronism and it is only under unusual circumstances that anysecondary clock would be so slow as not to be on time on the sixtiethminute.

It will be understood that if in any case it is required to correct thetime of the entire system, as for example, when the master clock isrunning fast or slow and this correction is to be within the rangepermitted by the synchronizing period it is only necessary to re set thehands of the master clock to the desired extent. The secondaries willthen set themselves within the next hour. If the amount is in excess ofthe synchronizing period for which the system is designed, for example,when a daylight saving correction is required, a manual control isbrought into operation as shown in Fig. 1 which will now be described.Referring to the diagram a wire 48 is provided tcrl'ninating in a switchpoint as shown. A switch mom )6! 49 is disposed in line 32 and for theusual running position is closed in the position shown. To retard thesecondary clocks the switch 49 is displaced to the open or off positionbreaking line 32 and also being out of contact with the switch point onwire 48. This switch is maintained open for the desired retardingperiod. If it is desired to advance the clock the switch 49 is thrown toconnect with the switch point or wire 48. The effect of connectingswitch 49 with wire 48 is to cause the fast set-up contacts 19 to comeinto action and rapidly advance the various secondary clocks. The switch49 will be held closed until the secondary clocks advance to the desiredextent. For example, to advance all of the clocks one hour with contacts19 closing every two seconds it will take two minutes to bring about theproper advance of the secondaries.

It will be understood that it is not essential to hold switch 49 closedfor the exact period inasmuch as the synchronizing system will functionto bring the clocks in time with the master clock whether the saidsecondary clocks are fast or slow with respect to the master clock. Itis only necessary that they be brought within the range of thesynchronizing period.

The above is equally true with regard to retarding operations it beingonly necessary to open switch 49 for approximately the desired retardingperiod.

While in the present embodiment we have selected a synchronizing periodof fifteen minutes, it will be understood that this period is givenmerely for purposes of illustration and that this period may be greateror less as desired. In convei'itional clock systems of the present daythis period has been found to be ample for all practical purposes.

In the present system it will be apparent that the master clock sendsout over a circuit normal impulses impressed under high voltage for adefinite period and then automatically shuts off the high voltage sourceof current and connects a low voltage source of current across the samecircuit for another period of time which corresponds to thesynchronizing period and during which normal and fast impulses are sentout. All of the apparatus necessary to produce this operation isself-contained in the master clock.

T he actuation and synchronization of the secondary clocks are dependentupon the strength of current received by them and their own chronologiccondition determines the utilization of the currents. The devices forgoverning their operation are self-contained in the secondary clocks,and each clock determines whether it shall receive normal impulses, fastimpulses, or whether it shall be connected so as not to receive anyimpulses for a time.

Certain broad features of the present invention are broadly claimed inthe copending application of James WV. Bryce, Serial No. 21.322, fiicdApril 20, 1925.

What we claim is:

1. In a synchronizing clock system, the combination of a master clock,means for controlling the distribution of electrical energy underdifferent differences of potential over a common circuit, a secondaryclock connected across said common circuit each secondary clock having atranslating device, and means responsive to a difference in potentialfor determining Whether the electrical energy from said common circuitwill be utilized for advancing the secondary clock.

2. In a synchronizing clock system, the combination of a master clock,means for controlling the distribution of electrical energy underdifferent differences of potential over a common circuit, means actuatedby said clock for controlling periodic excitation of said commoncircuit, a secondary clock connected across said common circuit eachsecondary clock having a translating device for actuating the same, andmeans responsive to a difference in potential controlled by saidtranslating device to determine whether or not said secondary clock willbe actuated by impulses caused by said periodic excitation of saidcommon circuit.

3. In a synchronizing clock system, the combination of a master clock, amain circuit, means for sending out over said main circuit a series ofnormal and rapid impulses periodically, a source of current having highpotential difference, a second source of current having low potentialdifference, means to de termine which of said two sources will supplythe current for said impulses, and means in the master clock to time andselect the sending of the impulses so that at least one impulse ofhigher potential difference is sent out by the master clock immediatelyfollowing the sending of the rapid impulses which impulses are of thelower potential difference.

4. In a synchronizing clock system, the combination of a master clock, amain circuit, means for sending out over said main circuit a series ofnormal and rapid impulses periodically, a source of current having highpotential difference, a second source of current having low potentialdifference, and means controlled by the clock for determining which ofsaid sources of current will excite said main circuit, said lastmentioned means having associated with it means for causing at least oneimpulse of higher potential difference to be emitted as a normal impulseimmediately following the emission of the rapid impulses, which rapidimpulses are emitted with a relatively lower potential difierence.

5. In a synchronizing clock system, the combination of a master clock,means controlling the distribution of electrical energy of differentvoltages, a secondary clock, a circuit for conducting said electricalenergy to said secondary clock, means interposed in said circuit forreducing the strength of the current flowing therethrough, and meanscontrolled by the chronologic condition of said secondary clock forchanging the relation of said means.

6. In a synchronizing clock system, the combination of a master clock,two sources of current under different differences of potential, asecondary clock, a secondary clock circuit electrically related to saidmaster clock, means controlled by said master clock for connectingeither one of said sources of our rent with said secondary clockcircuit, two branch lines in said secondary clock, a resistance in oneof said branches, and a switch for connectin either one of said branchlines in said secon ary clockcircuit.

7. In a secondary clock, the combination of a shaft, a ratchet wheel onsaid shaft, an electromagnet for actuating said ratchet wheel, twobranch lines, a resistance in one of said lines, a switch, and meanscontrolled by the position of said shaft for connecting either one ofsaid lines in series with the electromagnet.

8. In a secondary clock, the combination of electromagnetic actuatingmeans, and means including an electrical resistance for selectivelycontrolling the operation and nonoperation of said actuating means.

9. In a secondary clock, the combination of electromagnetic actuatingmeans for the clock hands, a resistance, a switch, and means controlledby the chronologic position of said clock hands for putting saidresistance into or. out of circuit with said electromagnetic means.

10. In a secondary clock, the combination comprising a main circuit forsupplying electrical energy, an electromagnetic actuating means in saidmain circuit normally operable, two branch lines, one of said branchlines having more electrical resistance thanthe other, and means forconnecting one or the other of said branch lines in series with saidelectromagnetic means.

11. In a synchronizing clock system, the combination of a master clock,a main circuit, a secondary clock, means controlled by said master clockfor controlling the distribution of electrical energy over said maincircuit, two sources of electrical energy having different differencesin potential, means for selecting from which one of the two of saidsources energy shall be derived, translating means for actuating saidsecondary clock, and means for determining whether the electrical energyfrom said main circuit will be utilized for advancing said secondaryclock. I

12. In a synchronizing clock system, the combination of a master clock,a main circuit, means controlling the distribution of electrical energyover said main circuit, a secondary clock, translating means in saidmain circuit for actuating said secondary clock, branch lines of saidmain circuit, one of said branch lines having more electrical resistancethan the other, and means for connecting one or the other of said branchlines in said main circuit.

13. In a synchronizing clock system, the combination of a master clock,a main circuit, a secondary clock, means for energizing said maincircuit by impulses at a normal rate and at a faster than normal rate,two sources of electrical energy having different differences inpotential, means for determining from which one of the two of saidsources of electrical energy shall be derived electrical energy for saidimpulses, electromagnetic means for actuating said secondary clock,"

two branch lines in said main circuit, and means for connecting one orthe other of said branch lines in circuit with said electromagneticmeans.

14. A secondary clock adapted to receive impulses of current over asingle line of different voltage characteristics at different times, anactuating magnet for actuating the clock step-by-step, and means forsuppressing the operation thereof upon the concurrence of the receptionby the clock of impulses of a given voltage with a certain chronologicalsetting of the clock itself. 15. The invention set forth in claim 14 inwhich means is provided for reinitiating the impulse advance of theclock upon the reception of an impulse of current of different voltageafter the operation of the magnet has been suppressed as a result of theineffectual effort of current impulses of other voltage.

16. A master clock for use in a synchronized clock system withprovisions for sending out over a line normal impulses and for sendingrapid impulses for a particular time period in combination with means inthe master clock forcausing the normal current impulses to be sent outwith a particular voltage characteristic, and means in said master clockfor causing impulses of a different voltage characteristic to be sentout during the said rapid impulse sending period.

17. A synchronized clock system including a single line circuit, amaster clock with provisions for sending normal impulses and fastimpulses over said single line, a secondary clock also connected to saidline, and means for effecting synchronization of the master andsecondary clocks, said means comprising,

.in combination, means in the master clock for varying the "oltage ofthe normal impulses with respect to the voltage of the fast impulses,and means in the secondary clock for selectively controlling theoperation thereof both in accordance with the chronological condition ofthe secondary clock and in accordance with the voltage character of theimpulses being sent over the line.

18. In a synchronized clock system with a master clock with provisionsfor sending normal and rapid impulses, a line circuit, and a secondaryclock with an operating magnet therein, in combination with means at themaster clock for sending impulses of variable voltage characteristics atvariable time periods, means in the secondary clock for coordinating theoperating magnet of the clock for operation or non-operation inaccordance with the conjoint control of the character of voltage of theimpulses which are being then sent out by the master clock and infurther accordance with the chronological condition of the secondaryclock.

19. The invention set forth in claim 18 in -which means is provided atthe secondary clock for reestablishing an operating condition of themagnet after the magnet operation has been suppressed, said means beingin condition for operation upon initial receipt of a current'impulse ofdifferent voltage after the receipt of impulses of current ofineffective voltages.

20. A secondary clock comprising in combination, time indicating means,electromagnetically actuated means for causing step by step advance ofsaid time indicating means, an electrical resistance device, and meanscontrolled by the chronological condition of the clock itself forcausing said resistance device to suspend advancement of said timeindicating means unless and until the energizing electromotive forcereceived by the clock is increased.

21. A secondary clock comprising in combination, time indicating means,electromagnetically actuated means including an impulse magnet forcausing step by step advance of said time indicating means, anelectrical resistance device, and means controlled by he chronologicalcondition of the clock itself for rendering said resistance deviceeffective to prevent sufficient current to flow through theelectromagnet of said impulse actuating means to advance the clockunless and until increased voltage is received by the clock.

22. A synchronized clock system comprising in combination a master clockand a secondary clock, the latter being of an impulse type andcomprising a common impulse magnet which by its own action effects alladvancing movements of the clock which are required for normal step bystep advance or for accelerating the clock if the same is slow andmaster clock controlled means for sending out impulses of varyingvoltage, and selecting means at the secondary clock for renderingeffective or ineffective the received impulses for driving the secondaryclock.

23. A synchronized clock system having a master clock and a secondaryclock of the impulse type and a single line circuit connect- 1ng thesame for operating and synchronizing the clocks and comprising incombination a common impulse magnet which is employed in the secondaryclock for both advancing the clock for normal step by step operationsand for accelerating it by step by step operations when it is slow, andsupplemental devices which are provided in the secondary clock forpermitting the passage of effective impulses to the impulse magnet orfor rendering ineffective impulses flowing to the magnet, said devicesexerting control conjointly in accordance with the voltage of theimpulses and in accordance with the chrono-" lo ical condition of thesecondary clock for e ecting synchronization of the secondary clock withrespect to the master clock and for permitting the advance of thesecondary clock in synchronization with the master clock.

24. A synchronized clock system including a master clock and secondaryclocks of the impulse type, each of the latter having a single impulsemagnet which effects all step by step advance of the clock both fornormal step by step advance and also for accelerating step by stepadvance when a clock is slow, and including in combination, a commonline circuit connecting the master and secondary clocks, means at themaster clock for sending out over the same common line circuit all thecontrolling impulses to the clocks which comprise a number of relatiiely low voltage regular impulses, more rapidly recurring acceleratingand relatively low voltage impulses and at a certain starting time asdetermined by the master clock one or more impulses of relatively highervoltage for reinitiating advance of the clocks, and means at eachsecondary clock including a resistance and switching device which latterdevice is controlled by the chronological condition of the associatedsecondary clock for suspending advance of the clock by rendering the lowvoltage impulses which are received ineffective to operate the impulsemagnet and for also permitting a reinitiated impulse advance of theclock upon the reception of the higher voltage impulses from the masterclock.

25. A synchronized clock system including a master clock and at leastone secondary clock of the impulse type, each secondary clock having acommon impulse magnet for advancing the clock for normal step by stepadvance and for accelerating the clock by step by step operations whenit is slow, and including in combination, a single line circuitconnecting the master and secondary clocks, each secondary clockincluding a resistance and switching means for effecting suspension offurther step by step advance of the secondary clock, said switchingmeans being controlled by the chronological condition of the secondaryclock itself, and said resistance being adapted under the control of theswitching means to prevent effective energization of the secondary clockimpulse magnet When impulses are received of a determined voltage fromthe master clock and when operation of the secondary clock is to besuspended, and means in the master clock including provisions forsending out over the same common line circuit a reinitiating impulse ofrelatively higher voltage than those previously sent to again causeeffective energization of the impulse magnet through the cooperatingresistance.

26. A synchronized clock system wherein the system comprises a masterclock and one or more secondary clocks, each secondary clock being ofthe impulse type and including an impulse magnet which effects all stepby III step advance of the clock whether for normal step by stepoperations or for rapid step by step accelerating operations when theclock is slow, and comprising in combination a single line circuit whichincludes an outgoing line and return line extending from the masterclock to the secondary clocks, each of the secondary clocks beingconnected in parallel relation to each other and each being connectedrespectively to the outgoing and return line, means at the master clockfor sending out over the common line circuit current impulses of acertain voltage for a number of normal impulses and for the faststepping up impulses and for also sending out subsequently over the samecommon line circuit at least one impulse of a higher voltage at acertain time as determined by the chronological condition of the masterclock, and cooperating means at each secondary clock comprising aswitching means and a resistance means adapted for cooperation with theimpulse magnet, the switching means being controlled by thechronological condition of the secondary clock, said switching means andresistance being adapted to suspend operation of each secondary clockwhen said secondary clock attains a certain time condition andwhile lowvoltage impulses are being received over the line circuit and forpermitting reinitiated advance of the clock upon the reception of ahigher voltage impulse over the same line circuit.

27. A synchronized clock system including a master clock, a secondaryclock, said secondary clock including an impulse magnet which efi'ectsall step by step advance of the clock including the normal advance andthe rapid step by step impulse advance for accelerating the clock, andincluding in combination, a single line circuit connecting the masterand secondary clock, means at the master clock for sending out all overthe same common line circuit a number of relatively low voltage impulsesand also a number of more rapidly recurring relatively low voltageimpulses for accelerating the secondary clock if slow, and alsoincluding means at said master clock for sending out over the samecommon line circuit beginning from a certain starting time as determinedby the chronological condition of the clock and which time is subsequentto the sending out of the low voltage impulses certain impulses ofrelatively higher voltage for reinitiating impulse advance of thesecondary clock after its operation has been suspended, and cooperatingmeans at the secondary clock adapted to receive over the same commonline circuit from the master clock the low voltage impulses both rapidand slow and the high voltage impulses, said means including aresistance and switching means cooperating with the impulse magnet inthe secondary clock with provisions for interrupting the step by stepadvance of the secondary clock at a certain time as determined by thechronological condition of the clock and while low voltage impulses arebeing received, and for permitting a reinitiated step by step advanceafter suspension of operation of the secondary clock and upon receptionof the high voltage impulses from the master clock.

28. A synchronized clock system including a master clock anda secondaryclock including in combination, means for sending out from the masterclock to the secondary clock a series of impulses of one voltage andalso impulses of a difi'erent voltage, means in the secondary clockcomprising an impulse magnet responsive to said impulses for causing alladvancing movement of the secondary clock, and means controlled by thechronological condition of the secondary clock and also responsive to adifference in voltage of the received impulses for rendering theimpulses of one voltage effective or inefi'ective to advance thesecondary clock by said impulse magnet.

29. A nized clock systems and comprising a common impulse magnet whichby its own action cffcets all advancing movements of the clock which arerequired for normal step by step advance or for accelerating the clockif the same is slow, with means at each secondary clock for suspendingits advance under certain chronological conditions of the clock, saidmeans comprising means for rendering received impulses ineffective, saidmeans being also variably effected by a received impulse of highervoltage to permit a reinitiated advance of the clock under the action ofthe impulse magnet after its action has been suspended, and meansincluding a single line circuit extending into the secondary clock fromthe master clock for sending thereinto from the master clock both thenormal and fast impulses which normally advance and accelerate the clockand for also transmitting thereto a current impulse of special voltagecharacteristics which upon its reception by the clock is adapted toreinitiate an advance thereof after its operation has been suspended.

30. A synchronized clock system including a master clock and a secondaryclock of the impulse type and a single line circuit connecting the samefor operating and synchronizing the clock and comprising in combinationa common impulse magnet which is employed in the secondary clock forboth advancing the clock for normal step by step operations and foraccelerating for step by step operations when it is slow andsupplemental selecting devices which are provided in the secondary clockfor suspending operation of the secondary clock and which devices areresponsive to current of. special voltage characteristics which is sentby the master clock to secondary clock for use in synchrothe secondaryclock over the common line circuit which transmits the normal and :fastimpulses for rendering the impulse magnet again efiective for o erationto advance the clock when the secon ary clock is to reinitiate itsadvance in synchronism with the master clock.

31. A secondary clock comprising in combination time indicating meansand step by step mechanism for operating the same, an electromagnetwhich operates and causes the step by step mechanism to advance theindicating means at a normal rate when the time indication is correctand at a rapid rate when the time indication is slow, means including aresistance and a switching means, the latter being operated by the stepby step mechanism when the time indicating means has reached apredetermined position for suspending operation for the step by stepmechanism by the electromagnet, and means responsive to concurrentenergization of said resistance device and electromagnet by current of avoltage characteristic different from that of the current which causedthe time indicating means to be brought up to said predeterminedposition for causing the electromagnet again to advance the timeindicating means.

In testimony whereof we hereto aflix our signatures.

JAMES W. BRYCE. CHARLES H. GETZ.

